It is known in the drilling of wells for hydrocarbons and other fluids to drive tubulars into an earthen formation, especially offshore into the seabed. In current practice, tubulars, which include conductor pipe, are driven by a pile driving apparatus, such as a pile driving hammer, from a point below a drilling rig floor to form a continuous string to a point in the earthen formation anywhere to a desired depth. This continuous string serves as conduit for the drilling activity and ensures that the upper portion of the well does not collapse. The string also serves as a conduit for fluids that are pumped down the well, as well as a support for subsequent casing strings or top side structure components.
“Drive shoes” refer to the bottom end of a string of conductor that is driven into the ground. In most cases, a drive shoe is merely an inverted bevel in the bottom end of the drive pipe. The inverted bevel helps to deflect the soil and reduce the end bearing when driving with a pile driving hammer. Other drive shoes are designed to push the soil or break up the soil formation. These drive shoes open a hole for the pipe, but the hole can cave in around the pipe due to soil pressure. When the hole caves in around the pipe, the friction between the soil and surface of the pipe make it difficult to drive the pipe deeper into the ground.
U.S. Pat. No. 4,657,441 (the '441 patent) teaches that soil is compressed and that such compression of the soil is unacceptable when using a drive shoe. The soil is compressed because, as the pipe is driven, both the soil at the inner diameter (ID) of the drive shoe and the soil at the outer (OD) of the shoe are compressed. The '441 patent also teaches breading up of the soil by having a series of ribs and a series of spiral inner bar sections on the OD to torsionally disassociate the soil, intermittently de-cohering the soil causing it to break up and become loose.